This invention relates to the art of wheeled load carriers and, more particularly, to improvements in wheeled load carriers which are provided with devices to facilitate displacement of the carrier upwardly and downwardly relative to a stairway.
The present invention finds particular utility and accordingly is described herein in conjunction with a portable, motor driven, drum-type drain cleaning machine. At the same time, it will be appreciated that the invention is applicable to any load carrier of the character having wheels for transporting a load along an underlying surface and with respect to which carrier it is desirable to facilitate the displacement thereof, with or without a load thereon, upwardly and downwardly relative to a horizontal edge elevated from the underlying surface.
It is of course well known to provide wheeled dollies, carts, hand trucks, portable machine supporting frames and the like with slide arrangements which facilitate sliding movement of the carrier upwardly and downwardly along a stairway. Such slide arrangements are disclosed, for example, in U.S. Pat. No. 5,087,013 to Gress et al wherein a foldable stand for a threading machine is provided with ridged skid bars, in U.S. Pat. No. 1,255,484 to Stephens wherein a portion of the frame of a wheeled truck for transporting garbage cans provides rigid skid bars, in U.S. Pat. No. 4,632,627 to Swallows wherein the underside of a wheeled loader, transport and work table cart is provided with glide bars, and in U.S. Pat. Nos. 4,364,139 to Babb et al and 5,031,276 to Babb et al wherein the supporting frame structure for a portable drum-type sewer cleaning machine is provided with skid strips. In each of the foregoing patents, the slide arrangement is defined by rigid skids or runners forming part of or fixed to the carrier. It is also known to provide such carriers with slide arrangements which are rotatably displaceable relative to the carrier as shown, for example, in U.S. Pat. No. 3,007,186 to Olsson wherein the supporting frame structure for a sewer cleaning machine is provided with a staggered wheel arrangement to facilitate displacement of the machine upwardly and downwardly along a stairway, and U.S. Pat. Nos. 3,246,354 to Cooney et al and 3,747,153 to O'Neill wherein the supporting frame for a portable sewer cleaning machine is provided with a belt-type slide arrangement in which a pair of endless belts are trained about and displaceable relative to corresponding underlying belt support members.
Slide arrangements of the foregoing character serve their intended purpose of making it easier to move a wheeled carrier and its load upwardly and downwardly relative to a stairway, but considerable difficulty is attendant to efforts of a workman to elevate or lower the carrier and load relative to a horizontal surface having an elevation greater than that of a riser of a stairway, such as a loading platform or the bed of a truck, for example. In this respect, the carrier must be positioned adjacent the horizontal edge of the platform or truck bed and then elevated and pivoted about the horizontal edge and pushed onto the horizontal surface against the resistance resulting from frictional engagement between the horizontal surface and the loaded carrier, whereby sliding of the carrier and load onto the horizontal surface is difficult to say the least, even when the slide arrangement is provided by rotatable belts or wheels as in the patents to Conney et al, O'Neill and Olson. Considering the fact that the load on the carrier can be 200 pounds or more, it will be appreciated that such loading and unloading of the carrier relative to an elevated horizontal surface can require the effort of two workmen and still require considerable physical effort on the part of the workmen to achieve the loading or unloading operation. In connection with portable sewer cleaning apparatus, it is not uncommon for a single workman to have to achieve such loading and unloading alone, and it will be appreciated that the physical effort required not only subjects the workman to potential injury through muscle strain but also through the difficulty in achieving the loading or unloading of the carrier and load without the latter slipping from the workman's hands and thus subjecting the workman to physical injury.
One effort to overcome the difficulty of loading and unloading portable drain cleaning apparatus relative to an elevated horizontal surface is disclosed in the aforementioned patent to Cooney et al wherein a wheel is provided at the upper end of the handle of the carrier. The wheel is adapted, upon pivoting of the loaded carrier about the horizontal edge of the elevated surface to engage the latter and allow the workman to elevate the lower end of the carrier relative to the horizontal surface in the manner of a wheelbarrow and then move the loaded carrier further onto the horizontal surface. A principal disadvantage of this arrangement is the instability of the loaded carrier during movement onto the horizontal surface resulting from the single wheel and the tendency of the carrier to pivot in opposite directions laterally thereof. Furthermore, the location of the wheel on the upper end of the handle interferes with a workman's grasping of the handle for rolling transport of the carrier and load along an underlying surface, and the wheel must be removed from the handle to avoid such interference.